This invention relates to impression materials, particularly for use in dental applications, which are formed by mixing a powdered material with water, as for example alginate impression materials or alginate substitute materials, i.e., those in which the alginic acid salt component is replaced by a substitute polymer, for example, carboxymethyl cellulose, xanthan gum, and the like.
Alginate impression and alginate substitute materials are known and have been used successfully for many years in the dental arts. See, for example, U.S. Pat. Nos. 2,345,255 to Gross; 2,390,137 to Vallandigham; 2,397,145 to vanBuren Joy; 2,422,497 to Noyes; 2,878,129 to Rabchuck; 3,246,998 to Higashi et al; Reissue 23,700 to Lockridge; and 2,733,156 to Cornell; the disclosures of these patents relevant to the preparation of conventional alginate and alginate substitute impression materials being incorporated herein by reference.
The use of such impression materials generally involves the proper measuring and then mixing of certain powdered constituents or components of the impression material (referred to hereinafter as the powdered components), with water or a substitute liquid, proper measuring of the powdered and liquid components being essential to obtaining satisfactory physical properties. Prior to mixing the powdered and liquid components, it is common practice for the user to shake the container in which the various powdered components of the impression material are stored to fluff them. This fluffing is done to facilitate the measuring or proportioning of the powdered components, using a scoop or ladle which usually is provided with the container. Under such circumstances, however, when the top of the container is opened, some of the fluffed powder tends toward dusting, i.e., becoming airborne and floating out of the container. Dusting also tends to occur when the powdered components are mixed with water or a water substitute due, at least in part, to the difficulty with which the powdered components are wet by the water. In practice, the powdered components are placed in a flexible mixing bowl and water is added to it. The powdered components do not wet immediately and the bulk of the powder floats for a period of time on the surface of the water during mixing, thus permitting some dusting to occur. The dusting problem is further exaggerated because the harder one stirs the powdered components/water mix, the greater is the opportunity for a portion of the powder to become airborne.
This dusting, which occurs primarily when a portion of the filler in the powdered components separates from the remaining powdered components and becomes airborne upon mixing or shaking, or upon stirring with the liquid component of the impression material has become the cause of concern because of its potential health hazard. (Woody, R. D. et al, JADA 94, 501, 1977). According, it is a principal object of the present invention to reduce the dusting that occurs when the filler in the powdered components separates and becomes airborne upon mixing or shaking.
It is another object of the present invention to achieve easier wetting of the powdered components by water or a substitute liquid.